1. Field of the Invention
The present invention relates to a reactive sputtering apparatus.
2. Description of the Related Art
A reactive sputtering apparatus adds a reactive gas such as oxygen or nitrogen to a discharge gas such as argon gas used in a normal sputtering apparatus to generate a compound thin film by the reaction of the reactive gas and sputter particles sputtered from a target material.
The reactive sputtering apparatus can easily form various compound thin films simply by adding a reactive gas to a normal sputtering apparatus, and is therefore often used in a process of manufacturing, for example, a semiconductor or an electronic component material these days. Japanese Patent Laid-Open No. 2004-156137, for example, discloses a thin-film forming apparatus which introduces both argon gas from a sputter gas introduction port provided in a vacuum chamber, and oxygen gas from an oxygen gas introduction port provided in the vacuum chamber.
Japanese Patent Laid-Open No. 5-247639 discloses a sputter apparatus that includes a deposition shield plate which defines a sputtering space in a vacuum chamber, and forms, on the surface of a wafer mounted on a wafer stage in the vacuum chamber, a thin film of metal particles sputtered from a sputter target provided in the upper portion of the vacuum chamber. This sputter apparatus includes an argon gas introduction port which introduces argon into the vacuum chamber, a reactive gas introduction port which directly introduces a reactive gas into the space defined by the deposition shield plate, and a manometer capable of measuring the pressure in the vacuum chamber.
In recent years, to generate a high-quality compound thin film with good reproducibility by reactive sputtering so as to meet a demand for an improvement in performance of devices, the conventional apparatus is not suitable for mass production in terms of pressure stabilization.
Hence, the inventor of the present invention closely examined the cause of this fact, and found out the following problem. That is, a deposition shield plate is normally provided in a processing chamber to prevent adhesion of the sputter material to the chamber. When this deposition shield plate is periodically replaced for maintenance, the pressure in the sputtering space defined by the deposition shield plate, the substrate holder, and the target fluctuates due, for example, to a mounting error of the deposition shield plate. This adversely affects the film quality, leading to degradation in yield.
Also, the sputter apparatus disclosed in Japanese Patent Laid-Open No. 5-247639 includes an argon introduction port which introduces argon into the vacuum chamber, and a reactive gas introduction port which directly introduces a reactive gas into the space defined by the deposition shield plate. Unfortunately, when a film adheres to a gas introduction pipe and peels off, it mixes in a substrate, leading to degradation in yield. Furthermore, the sputter apparatus according to Japanese Patent Laid-Open No. 5-247639 has an integrally formed deposition shield plate and gas introduction port, thus making it impossible to replace only the deposition shield plate having a film adhering on it. In other words, to replace the deposition shield plate, it must be replaced together with the gas introduction port. However, the replacement of the gas introduction port is impractical because the replacement process generates an error due to the differences between individual gas introduction ports or an error upon mounting the gas introduction port, and requires a lot of time and effort. On the other hand, if the deposition shield plate having a film adhering on it is continuously used for a long period of time, the film peels off the deposition shield plate, thus generating particles in the chamber.